On-Site Sewage
Rural Properties Usually Need a Septic System Permit
If your property is outside a city sewer system, you need a permitted on-site sewage facility — commonly called a septic system.
In rural parts of McLennan County, most homes use a septic system. State law calls these On-Site Sewage Facilities, or OSSFs. You must get a permit before you install or repair one. A local agent — usually the county or a city — issues the permit. The Texas Commission on Environmental Quality (TCEQ) oversees the whole process.
There is one exception. On a tract of 10 acres or more with a single-family home, you may not need a permit. To qualify, all parts of the system must be at least 100 feet from the property line. A licensed site evaluator must also approve the site. Check with McLennan County or TCEQ before you build on rural land.
Source to confirm: TCEQ — On-Site Sewage Facilities (Septic Systems)